Drilling submarine wells



April 22, 1941.

F. C. LAURIE DRILLING SUBMARINE WELLS Filed. Aug 31, 1939 WWW lag

(ZN/1 6. La UI"/ INVENTOR ATTORNEY.

Patented Apr. 22, 1941 DRILLING SUBMARINE'WEILS Frank C. Laurie, New York, N. Y., assignor to Standard Oil Development Company, a corporation of Delaware Application August 31, 1939, Serial No. 292,767 2 Claims. (Cl. 255-1) The present invention is directed to a method for drilling submarine wells, that is to say, wells under water, for the production of oil.

For the past several years, following the discovery of oil deposits under bodies of water, considerable thought has been given to the various problems encountered in the drilling of wells to such submarine deposits. Among the various problems involved is the problem of corrosion which arises by reason of the fact that the most of these deposits of oil are under salt water or brackish water which is highly corrosive. It is to this problem especially that the present invention is directed.

According to the present invention, a submarine well is drilled by first drilling into the bottom of the body of water from a derrick suitably mounted on piles or otherwise, a hole ranging from about fifty to about two hundred feet in depth and setting fairly large casing in this hole. This casing is cemented in the usual way up to the bottom of the body of water. The casing is of a length sufficient to extend above the surface of the water so that after it is cemented it thenceforth forms a water-tight passage between the derrick fioor and the formation to be drilled.

Due to the corrosive effect of the water outside the casing, however, it would be dangerous to rely only on this casing to protect the future drilling operations because at a later stage a break in this casing admitting the water from the surface body into the bore hole would be extremely d. Accordingly, therefore, the bore hole is drilled mrther several hundred feet, ranging from about six hundred to a thousand feet, and smaller casing is then set inside the larger casing. Cement is then poured down into the inner casing and up through the annular space between the two casings until it overflows at the upper end of the outer casing. The'cement is then allowed to set. The result is a tubular passage having two metal walls separated by a cement wall. Corrosion of the outer metal wall can result in no damage because the cement is resistant to corrosion.

The present invention will be better understood from the following detailed description 01' the accomn r s'drawing in which Fig. l is a vertical section of a. well drilled in accordance with the present invention after'the setting of the first casing; and

4 on the floor 5 of which is mounted the customary rotary table 6 in which is shown a drill stem 1 carrying a drill bit 8. It will be understood that the derrick and the drilling equipment are shownsketchily only for purposes of illustration.

A bore hole 9 has been drilled into the earth and a casing ll set into the bore hole with its upper end protruding above the surface of the body of water 2. Cement has been forced into the casing and up around its outside to form a cement wall II. The cement'is held in place until it is set by the usual plug l2.

After the cement has set the drill bit is lowered and the plug l2 and the cement'beneath it drilled away and drilling of the bore hole is continued until a depth of approximately six to eight hun-' dred feet is reached. It will beunderstood that this depth may vary to a large extent, depending upon the circumstances. For example, if a troublesome water sand were encountered at a depth of two hundred feet, the hole would be drilled to a point where this formation could besealed oil by cementing. Usually, the depth to which the hole is drilled in this second stage will be dictated by the depth of the water formations which must be sealed oil.

When the hole is drilled to the desired depth, a

second string of easing l3'of smaller diameter Fig. 2 is a similar figure after the setting of the second casing.

Referring to the drawing in detail, numeral l tea the earth under a body of wateri.

than string M is lowered into the bore hole with its upper end extending above the upper end of string to. In practice, the string ll will have a diameter of about 13" or slightly larger, and string II will have a diameter of about 11". Cement is then forced down through the inside of string is and up through the annular space between strings Ill and I3 until it overflows at the upper edge of string 10. This cement is then allowed to set in the usual way and drilling is continued.

In actual practice, before the continuation of the drilling, blowout preventors will be fixed to the upper end of casing l3. In some instances before the oil formation is reached a second troublesome water formation may be encountered in which case another string of casing is set, of smaller diameter than string ii. In this event cement need be forced outside of the third stringof casing only a sufiicient distance to seal oi! the water formation and need not be forced up to the upper end of string II. It is customary in this case, however, to have the smaller string extend above string II and to place the blowout controls on the smaller string.

Embedded in the earth and extending above the The nature nd obiecis of th p ent inven ion having been thus described and illustrated, what is claimed as new and useful and is desired to be secured by Letters Patent is:

1. In the completion of an oil well under .a body of water the steps which comprise drilling a bore hole a substantial distance into the earth. below the water, setting casing in said bore hole of sufficient length to have its upper end extend above the surface of the water, keeping said upper end independent or the means used for drilling, filling with cement the space in the bore hole between the casing and the earth, continuing the drilling through said casing to extend said bore hole a substantially further distance into the earth, setting into said extended bore hole a second casing of such a smaller diameter than the first that an annular space is created between them, such second casing being otsumcient diameter to be used as a conduit for drilling equipment for further drflling, forcing cement into said annular space up to the top of the outer casing, allowing said cement'to set, and then proceeding with the drillingoperations through the second casing.

2. In the completion of an oil well under a body I of water the steps which comprise drilling a bore hole a substantial distance into the earth below the water, setting casing in said bore hole of sutflcient length to have its upper end extend above the surface of the water, keeping said upper end independent of the means used for drilling, filling with cement the space in the bore hole between the casing and the earth, continuing the drilling through said casing to extend said bore hole through at least one water-producing formation a substantial distance below said casing, setting a second easing into said extended bore hole, the diameter of said second casing being suflicient to allow it to be used as a conduit for drilling equipment for further drilling, and to create an annular space between said first and second casing, forcing cement into said annular space up to the top of the outer casing, allowing said cement to set and then proceeding with the drilling operation through the second casing.

FRANK C. LAURIE. 

